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Phase sampling techniques using amplitude bits for digital receiversRelated Patent Categories: Pulse Or Digital Communications, ReceiversPhase sampling techniques using amplitude bits for digital receivers description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070041472, Phase sampling techniques using amplitude bits for digital receivers. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of, and claims priority to, U.S. Utility patent application Ser. No. 10/036,788, filed on Dec. 21, 2001, entitled "Phase Sampling Techniques Using Amplitude Bits for Digital Receivers," by inventors Charles P. Norman and Charles R. Cahn, the entire application of which is incorporated by reference into this application, and also claims priority to Provisional Patent Application Ser. No. 60/257,663, filed on Dec. 21, 2000, entitled "Phase Sampling Techniques Using Amplitude Bits for Digital Receivers," by inventors Charles P. Norman and Charles R. Cahn, the entire application of which is incorporated by reference into this application. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates in general to digital receivers, and in particular to a method and apparatus for phase sampling using amplitude bits for Global Positioning System (GPS) receivers. [0004] 2. Description of the Related Art [0005] Digital receivers are typically very complex devices that locate weak signals in sometimes difficult signal acquisition environments. Currently, federal government mandates for and interest in producing digital receivers, specifically digital GPS receivers, that are compatible with cellular telephones stems from a new Federal Communications Commission (FCC) requirement that cellular telephones be locatable within 20 feet once an emergency call, such as a "911" call (also referred to as Enhanced 911 or "E911") is placed by a given cellular telephone. Such position data assists police, paramedics, and other law enforcement and public service personnel, as well as other agencies that may need or have legal rights to determine the cellular telephone's position. Further, GPS data can be used by the cellular user for directions, location of other locations that the cellular user is trying to locate, determination of relative location of the cellular user to other landmarks, directions for the cellular user via internet maps or other GPS mapping techniques, etc. Such data can be of use for other than E911 calls, and would be very useful for cellular and PCS subscribers. [0006] Typically, digital receivers use a phase-sampling technique to detect zero crossings of the incoming signal, and attempt to align or correlate these zero crossings with a local oscillator or crystal. This allows the receiver to "lock" onto the received signal and use the signal for tracking, position determination, and other information. However, the use of phase information alone makes the correlation between the incoming signal and the reference signal difficult and more time-consuming, which could leave an E911 caller in a dangerous situation longer than necessary. Further, the typical phase-sampling technique requires significant power consumption for smaller, hand-held devices such as cellular telephones. [0007] Further, digital receivers are sometimes used in environments where Continuous Wave (CW) jamming is occurring, such as battlefields, congested signal areas such as airports, etc. CW jamming will degrade the receiver performance of the digital receiver, sometimes to the point where the digital receiver can no longer receive signals with any reliability. This could be dangerous for E911 callers that were unfortunate enough to be stranded in a location that is within a CW jamming area, as well as being potentially deadly for soldiers that are in a CW jamming area. [0008] It can be seen, then, that there is a need in the art for a method and apparatus for improved phase-sampling techniques that can reduce the complexity of the digital receiver circuitry. It can also be seen that there is a need in the art for reducing the power consumption for phase-sampling and correlating within the digital receiver. It can also be seen that there is a need in the art for integrating GPS and cellular devices in such a manner that reduces the time required to obtain position information. It can also be seen that there is a need in the art for a method and apparatus that can help overcome CW jamming problems for digital receivers. SUMMARY OF THE INVENTION [0009] To minimize the limitations in the prior art, and to minimize other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and an apparatus for phase sampling using amplitude bits for Global Positioning System (GPS) receivers. The phase sampling allows the digital receiver to avoid complex multiplication and instead performing a phase subtraction to derotate the phase of the incoming signal. [0010] A method in accordance with the present invention comprises downconverting the incoming signal to an Intermediate Frequency (IF) signal, running a counter at a higher frequency than that of the IF signal, outputting a state of the counter when the IF signal has a zero crossing, outputting a state of a magnitude of the IF signal when the IF signal has a zero crossing; and extracting the phase of the IF signal from the outputted state of the counter and the outputted state of the magnitude. [0011] It is an object of the present invention to provide a method and an apparatus for improved phase-sampling techniques that can reduce the complexity of the digital receiver circuitry. It is a further object of the present invention to provide a method and apparatus for reducing the power consumption for phase-sampling and correlating within the digital receiver. It is a further object of the present invention to provide a method and an apparatus for integrating GPS and cellular devices in such a manner that reduces the time required to obtain position information. It is another object of the present invention to provide a method and an apparatus that can help overcome CW jamming problems for digital receivers. [0012] Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. BRIEF DESCRIPTION OF THE DRAWINGS [0013] Referring now to the drawings in which like reference numbers represent corresponding parts throughout: [0014] FIG. 1 illustrates a flow chart illustrating one embodiment of steps that can be used in practicing the present invention. DETAILED DESCRIPTION [0015] In the following description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Overview [0016] The present invention uses at least one amplitude bit to assist the phase-sampling technique used in digital receiver architectures. Although described herein as applying to GPS receivers, the present invention can be used with any digital receiver that uses phase-sampling. [0017] Phase-sampling in digital receivers typically samples zero crossings at the Nyquist rate (i.e., the predetection bandwidth) to extract the phase of a narrow band signal with respect to an arbitrary reference. Such a technique is described in "Digital Phase Sampling for Microcomputer Implementation of Carrier Acquisition and Coherent Tracking" by Cahn, which is incorporated by reference herein. [0018] For some GPS receiver frequency plans, and other digital receivers where the Intermediate Frequency (IF) is a small integer multiple of the fundamental frequency f.sub.0, the present invention provides reduced processing complexity and reduced power consumption. The present invention works well with larger integer multiples of the fundamental frequency f.sub.0, with less dramatic improvements. The present invention allows the digital receiver to avoid performing coordinate rotation at high speeds, and replaces such a coordinate rotation with a simple phase subtraction. This replacement of the coordinate rotation allows the receiver to use a less complicated design, and to use lower power as a result. Continue reading about Phase sampling techniques using amplitude bits for digital receivers... Full patent description for Phase sampling techniques using amplitude bits for digital receivers Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Phase sampling techniques using amplitude bits for digital receivers patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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